The invention is directed to a process for the racemization of N-acetyl-D(L)-.alpha.-aminocarboxylic acids by heating their melts at high temperatures.
Such N-acetyl-D(L)-.alpha.-aminocarboxylic acids are obtained in the form of their salts in the enzymatic hydrolysis of the salts of N-acetyl-D,L-.alpha.-aminocarboxylic acids by means of an L-aminoacid acylase. They consist predominantly of N-acetyl-D-.alpha.-aminocarboxylics and in addition can also contain small amounts of the corresponding N-acetyl-L-.alpha.-aminocarboxylic acids. They are generally racemized after separation of the L-.alpha.-aminocarboxylic acid formed in the hydrolysis and employed again for the enzymatic cleavage.
It is already known to racemize N-acetyl-D(L)-.alpha.-aminocarboxylic acids by heating their melts to high temperatures. However, to obtain a complete racemization, relatively large residence times are required which lead to a strong discoloration and to the formation of considerable amounts of decomposition products.